Topic: check engine light

[signguy]

so i have a 92 22re pickup, the ecu went bad... i got another one and installed it and the check engine light was on and never went off. i found out that the truck i got the replacement ecu from was a California truck and was meant to have 2 o2 sensors and my truck only has one. is there a way to trick the ecu by jumping out pins or something to make the light go off? I'm not installing another sensor and i need the light to go out for inspection.  any help would be awesome

[yotaneck13]

pull your dash out and take the bulb out of the back of the guage cluster

[signguy [OP]]

Uh, no. I want it to be fixed right so the light comes on when something goes wrong, and it won't pass inspection without a check engine light. That's one of the things they check. 

[twistedtoy92]

should be able to wire in a resister to trick the ecu... I'm not sure how many OHM's though.....

[yotaneck13]

they check to see if the bulb is in there? if the light isnt on here then it passes it would be a temp fix to get it past them pesky inspections

[signguy [OP]]

yea they make sure that the light works, if it doesnt it fails! a resistor is not a bad idea, i should be able to read the ohms from the o2 sensor i have i guess? ill have to investigate

[yotarunner85]

Uh, no. I want it to be fixed right so the light comes on when something goes wrong, and it won't pass inspection without a check engine light. That's one of the things they check. 

If you want it fixed right then put the correct ECU in your truck. I don't think a resistor will work because the signal the ECU gets from the O2 sensor varies from 0 to 1 volt. If the Ecu doesn't see a varing voltage from the O2 sensor it will turn the engine light on.

[twistedtoy92]

if it has a constant medium then it will compensate the fuel/air mixture as needed. it will work. people do it all the time!
 find out what the resistance is, go to radioshack and get the proper resistor, wire it in so its not obvious and BAM you've got it taken care of. Voltage doesnt need to be varying to keep the light off. One is pre and the other is post, just measures the before and after 02 corresponding to the CAT. then you will have a constant ratio.

[yotaneck13]

if it has a constant medium then it will compensate the fuel/air mixture as needed. it will work. people do it all the time!
 find out what the resistance is, go to radioshack and get the proper resistor, wire it in so its not obvious and BAM you've got it taken care of. Voltage doesnt need to be varying to keep the light off. One is pre and the other is post, just measures the before and after 02 corresponding to the CAT. then you will have a constant ratio.

not to thread jack but could this be done to delet the 02 sensors from the system like so i wouldnt have to run them but the motor still run right?

[yotarunner85]

if it has a constant medium then it will compensate the fuel/air mixture as needed. it will work. people do it all the time!
 find out what the resistance is, go to radioshack and get the proper resistor, wire it in so its not obvious and BAM you've got it taken care of. Voltage doesn't need to be varying to keep the light off. One is pre and the other is post, just measures the before and after 02 corresponding to the CAT. then you will have a constant ratio.

I don't think it will work because the ECU reads voltage from both O2 sensors 0 to 1 volt. Adding a resistor in place of an O2 sensor you run the risk of damaging the ECU with a higher than 1 volt signal. Without an O2 signal you will get a code 27 for the 2nd O2 sensor. Here is a quote from the Shop Manual "
PURPOSE
The oxygen sensor is an exhaust mounted measuring device for determining the oxygen content in the exhaust gases. Since the amount of oxygen in the exhaust indicates precisely how complete the combustion of the air/fuel mixture in the cylinders is, it is also a good indicator of the air/fuel ratio.

OPERATION
The voltage signal generated by the OS is sent to the ECU through terminal OX1. The ECU uses this signal to enrichen or lean the fuel mixture accordingly. The higher the voltage output by the OS, the richer the sensed signal to the ECU and the more the ECU will lean the fuel input. The lower the voltage output by the OS, the leaner the sensed signal to the ECU and the more the ECU will increase injection pulse width. This will enrich the air/fuel mixture to the engine.

Certain models utilize a sub oxygen sensor in conjunction with the main oxygen sensor. The Sub-OS inputs a simultaneous voltage signal to the ECU through terminal OX2. Some oxygen sensors are equipped with internal heater elements to aid with efficiency and faster sensor warm-up."

You can bypass certain sensors with a resistor. For example you removed the EGR system, the EGR solenoid can be bypassed with a resistor the same resistance as the solenoid since the solenoid has a fixed resistance. Without the correct O2 signal the ECU will not function properly. I recomend Installing the correct ECU than wasting time trying to bypass sensors to get the light to turn off.

[yotarunner85]

not to thread jack but could this be done to delet the 02 sensors from the system like so i wouldnt have to run them but the motor still run right?

Yes, you can delete them. No, it will not run right. The ECU does have a preset strategy to run the engine if it doesn't get a signal from the O2 sensors, but it won't run very well. The O2 sensors are a good thing and are used to keep the engine running at the best fuel ratio.